An elevator shaft is the space enclosed by fireproof walls and elevator doors for the travel of one or more elevators. An elevator shaft has the pit disposed at the bottom end of the shaft and terminates with an overhead disposed at the top end of the shaft.
There are safety requirement that must be followed, when installing an elevator, with regards to the pit and overhead clearances. In particular, when installing a new elevator, overhead and/or pit clearances are provided by rules EN 81-1 and EN 81-2 in Europe and ANSI A17 in the US. And this is as an important and not to be ignored point about safety, as difficult to solve from a technical point of view.
While it is possible (though unlikely) for an elevator's cable to snap, all elevators in the modern era have been fitted with several safety devices which prevent the elevator from simply free-falling and crashing. An elevator cab is typically borne by a set of hoist cables, each of which is capable on its own of supporting the full load of the elevator plus twenty-five percent more weight, with a minimum safety factor 12. In addition, there is a device, typically called the governor, which device detects whether the elevator car is descending or ascending faster than its maximum designated speed. Upon such detection, the governor activates an emergency safety gear, which is an integral part of the car frame, thereby stopping the elevator car quickly, but not so abruptly as to cause injury.
According to elevator law/standards, every passenger elevator must be equipped with a safety gear to prevent free fall of the car, which safety gear, when activated, activates a mechanical lock to lock up the car onto the elevator's guide rails. In order to properly activate the safety gear, every passenger elevator must be equipped with an over speed governor (OSG), which governor senses whenever the car speed exceeding its designated speed, the OSG activates the safety gear device. Such activation results with a mechanical lock up of the car to onto the elevator's guide rails.
It should be noted that in some cases, the OSG is being used as an anti creeping device, preventing the car from unintended movement (“creeping”) in either direction. In such cases, the OSG is being electrically activated by means of a solenoid, and in order to allow normal use of the elevator, the anti creeping solenoid must be electrically energized. That is, whenever the car moves with a de-energized solenoid, the safety gear is automatically activated.
The required safety clearance, between the pit floor and the external bottom surface of the elevator's floor, is designed to prevent a crushing or squeezing of person and to enable a maintenance person, located at the pit, to survive a free fall or unintended movement of the elevator. That safety clearance is quite large and is often difficult to provide the required safety clearance, for example, in an existing building to which an elevator is to be added.
Therefore, there is a need for a safety mechanism for an elevator pit having a reduced safety clearance. Some safety mechanisms for an elevator pit with reduced safety clearance exist in the market. For example, European Patent EP 0725033 shows an elevator car blocking device, mounted in the pit, working directly on the bottom of the elevator car or on the counterweight, and suitable for creating a temporary working place at the pit or at the overhead, respectively. Although being functional and safe, the proposed mechanism is cumbersome, requiring a lot of space not always available in the pit for its double application, which would be quadruple in case of contemporary reduced pit and head, considering that traditional shock absorbers are already present in the pit. The reduced height requires the installation of a supporting pillar to obtain a height allowing a person entrapped to leave the pit and not only to take cover. Furthermore, the proposed mechanism is electrically complex, requiring a special harness to be combined with the elevator control board harness However, the proposed mechanism must be activated manually before entering the shaft and after exiting the shaft.
In another example, European Patent EP 1422182 provides a mechanism that activates the emergency safety gear of an elevator, having a reduced pit, when the distance between the bottom of the elevator car and the bottom of the pit decreases under a minimum safety value, wherein the operation of releasing and/or retracting said mechanism is made by a remote manual operation, performable from outside the elevator shaft. However, the proposed mechanism must be activated manually before entering the shaft and after exiting the shaft.
There is a need for and it would be advantageous to have a mechanism that activates the emergency safety gear of an elevator, whenever a person is in the pit of an elevator shaft or in the overhead of an elevator shaft.
A reduced pit also requires an apron that fit the height of the pit. In general, an apron (also called toe guard) is a safety device which is securely attached to an elevator car and forms a wall extending downwards from the elevator car, on the door side. Should the elevator car stop between floors, a gap is formed between the car and the landing floor, exposing the shaft. The apron is intended to cover the gap and thus prevent a person escaping from the car onto the landing floor, from falling through the gap into the shaft, as well as prevent any body part of a passenger from getting between the car and the landing floor. An apron suited for a reduced pit is in itself very advantageous as it facilitates a very low pit height.
There is therefore a need and it would be advantageous to have an apron that can fold when approaching the pit floor of an elevator shaft.